In the title compound, C(15)H(12)O(4)·H(2)O, the two benzene rings are not coplanar, making a dihedral angle of 7.24 (16)°. An intra-molecular hy-droxy-carbonyl O-H⋯O hydrogen bond occurs. In the crystal, four inter-molecular O-H⋯O hydrogen bonds involving the hy-droxy residues, the carbonyl group and the water mol-ecule lead to the formation of a three-dimensional network. The supra-molecular structure is further stabilized by weak C-H⋯O inter-actions.